Carbon-Based Cell Phones on the Horizon

-- The ability to generate tiny three-dimensional objects using a special printer just got a whole lot faster.
Machines, known as two-photon lithography printers, can produce detailed structures as small as a grain of sand.
Vienna University of Technology researchers Jan Torgersen and Peter Gruber, led by materials science and technology professor Jürgen Stampfl, took the printing process from millimeters per second to five meters per second, a world record.
This 3-D printed version of St. Stephan's Cathedral in Vienna is about 50 micrometers wide on its largest side, smaller than the diameter of the average human hair.

The printing process works by focusing a laser beam onto liquid resin. Mirrors guide the beam to solidify lines of the resin into solid polymer. Line by line, a layer is built. Each structure consists of numerous layers.
The scientists use a new resin, developed by chemistry professor Robert Liska, that could be solidified anywhere, not just on top of the previous layer. They also used faster electronics and rotating mirrors that had improved steering.
This is a 3D image of the "Wormser Tor," the city gate leading into the historic German town Frankenthal, which was first settled in the 8th century.
The scientists designed it from original photographs and their resulting print has never been published until now, Torgersen told Discovery News.

This race car is about 285 micrometers wide, according to Torgersen. While still small, it's several times the width of a human hair.
In the field of two-photon lithography printing, he calls their record-breaking printer a significant step closer to real applications and commercialization.

The goal was to speed up the process in order to make this type of printing more attractive as a technique, as well as more cost-effective.
Usually the speedy printer was occupied with the scientists' experiments instead of producing recognizable images, Torgersen said. But they did have some fun in demonstrating its capabilities, like this image of a man.
Tiny, intricately printed 3-D structures could have a number of different applications. For example, they could be used in medicine to make scaffold for living cells in order to build tissue.

Here, they replicated the Tower Bridge in London. Torgersen said he and his colleagues plan to focus on water-based biopolymers for biological applications. They currently have a paper on using hydrogels for the printing process under revision.
"We hope we can motivate potential partners from the biology side to work with us," he said.

Jan Torgersen and Peter Gruber
Researchers Jan Torgersen (left) and Peter Gruber (right) stand next to the printer.
The printer is part of a project called Phocam to develop new 3-D printing technology with industry partners.

PHOTOS: Extraordinary Beauty of the NanoArt World

One of the biggest knocks against cell phones is they require small amounts of rare earth elements: gallium, indium and arsenic, for example that are both scarce and expensive. But what if you could make a phone out a more common element, like carbon?

Researchers are taking slow, but sure steps toward building the innards of a cell phone out of carbon nanotubes, a structure that resembles a microscopic sheet of chicken wire rolled into a cylinder. These cylinders can be used to either conduct electricity or to store energy.

At the Technical University of Denmark, Jakob Wagner and colleagues has found a better way to build carbon nanotubes that could lead to their use as a semiconductor, a key component of all electronic circuit parts found in both cell phones and laptops. Carbon nanotubes have properties of both a metal and a semiconductor, depending on how they are rolled.

“The breakthrough here is that we are able to control the production of nanotubes whether they are metallic or semiconducting,” Wagner said from Copenhagen. “That’s important because if you want to use them in cell phones, we have to make sure they are either one or the other. The prospect is to use semiconducting carbon nanotubes as a substitute for gallium.”

Warner published his work earlier this month in the Nature publication Scientific Reports.

The next step is to be able to produce large amounts of semiconducting carbon nanotubes that could be made into an electronic device, Wagner said.

“The next challenge is incorporating the material into the devices,” he said. “It will not be tomorrow, let’s say 10 years.”

But at IBM, researchers like James Hannon are working to speed up that lab to prototype timescale. Hannon says that Wagner’s finding is an important step, but it needs to be replicated on larger diameter carbon nanotubes.

"This is a nice scientific demonstration but not in the range that would be used in a logic application," said Hannon, manager of IBM’s carbon electronics group in Yorktown Heights, N.Y. "I’d like to see if this technique could work for larger diameter tubes as well."

Last year, Hannon and his IBM colleagues announced they had built memory and microprocessing chips using carbon nanotubes. He said the tough thing is getting them to lie down in straight lines, but they overcame this obstacle by creating special grooves etched into the silicon chip surface and a bonding agent.

Hannon says the two challenges with carbon nanotubes is figuring out how to place them and how to separate the semiconducting ones from the metallic ones, which are thrown away. A separate team at North Carolina State University recently reported they were able to integrate carbon nanotubes into a flexible scaffold for a silicon-based battery that would last longer than existing lithium ion batteries.

Hannon says he expects carbon nanotubes to play a big role in electronic devices in a few more years of testing.

"Our mandate is that this stuff has to be ready pretty soon,” Hannon said. “We have to ready manufacture this."